Environment.TickCount is not enough

Question

I want to know on when was the last time the system was started.

Environment.TickCount will work but it is breaking after 48-49 days because of the limitation of int

Answer 1

The following code retrieves the milliseconds since system start (call to unmanged API). I measured the performance costs for that interop operation, and it is quite identical to StopWatch() (but that doesn't retrieve the time since system start directly of course).

using System.Runtime.InteropServices;

...

[DllImport("kernel32.dll") ]
public static extern UInt64 GetTickCount64();

...

var tickCount64 = GetTickCount64();

https://msdn.microsoft.com/de-de/library/windows/desktop/ms724411(v=vs.85).aspx